^^ AKlSrULAB OPEECULTJM. 



an examination of tlie different species, however, it will be found 

 that this is quite unsatisfactory, as a generic distinction ; because 

 the same species which have short flattened spires, do not always 

 have angulated apertures. An example of each from IS". America 

 is represented, PL xiv. fig. 314. 



ANCTLUS. Geofiroy, 1767. Fam. Calyptracea, Lam. Otides, 

 Bl.— Desc/*. Thin, obliquely conical, patelliform; apex acute, 

 turned sidewise and backwards ; aperture oval ; margin simple. 

 — Obs, Although the little fresh-water shells described under 

 this name, resemble those of the genus Patella, the animals which 

 produce them are nearly allied to Lymnea. And, it may also be 

 observed, that the shells themselves differ from Patella in not 

 being quite symmetrical, having the apex turned on one side. 

 A. fluviatilis, PL xiii. fig. 246. PL xxiv. figs. 510, 511. 



ANDEOMEDES. Montf. Yoeticialis, Dam. Fam. Nautilacea, 

 Lam. A genus of microscopic Foraminifera. 



ANELASMA. Darwin. Cirrip. P. 169. A genus of pedunculated 

 Cirripedes distinguished from Alepas in important respects, 

 but like in having no shell. 



ANGrULITES. Montf. A genus composed of species of fossil 

 Nautili, described by De Blainville as not umbilicated, with a 

 dorsal keel and angular aperture. Nautilus triangularis, Buffbn. 



ANGIOSTOMATA. Bl. The third family of Siphonobranchiata, 

 Bl. described as differing little from the family of Entomostomata, 

 but having long, narrow, straight apertures, and the columeUar 

 lips straight or nearly so. Were it not for the admission of the 

 genus Strombus into this family, it would correspond with 

 CoLUMELLAEiA and CoKVOLUT^ of Lamarck. 



ANNELIDES. The ninth class of invertebrated animals, divided 

 into three orders, namely, A. Apodes, A. Antennes, and A. 

 Sedentaires. The last only contains families of testaceous Mol- 

 lusca. The animals are vermicular, some naked, others inhabiting 

 shelly tubes. See Sedentary Annelides. 



ANNUL AE OPEECULITM is one which has the nucleus central, 

 or nearly so, the other layers surrounding it in flattened rings. 

 The term concentric is also applied. See Introduction. 



